This will mostly concern those who are installing fiberglass front fenders for the first time, and need to cut out a slot for passage of the windscreen post. These photos are supplied by Francis Yerbury in France.

Right side above, left side below.

In inches the dimensions are, 3-3/4" from back edge of fender, slot 2" long and 11/16" wide (from mounting surface). Thus will be covered by a large rubber grommet, so it doesn't hurt to be slightly larger to allow alignment of the fender during installation.